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PHYSICS REVISION Full topics Question1. a. Write down the gravitational unit of force. How is it related to Newton? b. A water pump raises 50 litres of water through a height of 25 m in 5 s. Calculate the power which the pump supplies. [Take g = 10 Nkg 1 and density of water = 1000kgm 3] [Ans: 2500W] c. Name the three classes of levers and distinguish between them. Give two examples of each. d. A man weighs 600 N on the earth. What would be his approximate weight on the moon? What is the reason for your answer? [Ans: 100N; weight on moon is one sixth the weight on earth] e. Give an example when work done by the force of gravity acting on a body is zero even though the body gets displaced from its initial position. Question2. a. If the power of a motor is 40 kW, at what speed can it raise a load of 20,000 N? [Ans: 2m/s] b. A ray of light, after refraction through a concave lens emerges parallel to the principal axis. Draw a ray diagram to show the incident ray and its corresponding emergent ray. c. Draw a diagram to show how a converging lens can form a real and enlarged image of an object. d. Water is used in hot water bottles for fomentation. Give reason for this. e. How is the kinetic energy of a moving cart affected if (i) its mass is doubled, (ii) its velocity is made equal to speed of light. [Ans: (i) if mass is doubled kinetic energy doubles. (ii) if velocity is made equal to speed of light the kinetic energy would be maximum] Question3. a. State two application of an echo. b. How does the resistance of a wire depend on its radius? Explain your answer.
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